Compensated pilot-controlled thermostat



25, 1936- N. T. BRANCHE ET AL COMPENSATED PILOT CONTROLLED THERMOSTAT Filed NOV. 1, 1934 fA/vf/vrona /V.7T Era/7cm? 1/0. 59am {Z04 ATTORNEY Patented Feb. 25, 1936 COMPENSATED PILOT-CONTROLLED THERMOSTAT Nelson T. Branche and Vilynn 0. Beam, Toledo,

Ohio, assignors to Surface Combustion Corporation, Toledo, Ohio, a corporation of New York Application November 1, 1934, Serial No. 751,003

5 Claims. (Cl. 158-1171) This invention relates to safety mechanism for fluid fuel burners and more particularly to pilotcontrolled thermostats.

Thermostats which are controlled by a flame from a pilot are usually located in a heated environment the temperature of which adversely affects the operation of an ordinary thermostat by delaying its operation after the pilot ceases to function properly.

The present invention has for its object to provide a pilot controlled thermostat which shall be unaiiected in its operation by the temperature .of the environment where it may be located or in other words, to provide a thermostat which shall embody means for compensating for the temperature of said environment to the end that the thermostat may be quickly responsive to improper functioning of the pilot.

The various features of novelty and invention and other objects of the invention will more fully appear from the detailed description taken in connection with the accompanying drawing forming part of this specification and wherein the preferred form of the invention is shown.

Referring to the drawing,

Fig. 1 shows the improved pilot-controlled mechanism combined with gas burning apparatus associated with a house-heatingiurnace;

Fig. 2 is a perspective view of the said thermostat and other apparatus; V

Fig. 3 is view showing parts associated with the thermostat;

, Fig. 4 is a section to larger scale taken on line 33 of Fig. 3, and 1 Fig. 5 shows a modified form of construction of a detail.

In the drawing, A indicates the lower part of a domestic furnace; B a heating burner positioned therein; C a casing through which secondary air is supplied to the burner; D a cover for an electric motor diagrammatically indicated at M in Fig. 3, thefunction of the motor being to operate the main gas valve, not shown, for the burner B; .E a tube for supplying a mixture of air and gas to said burner; F a pilot for lighting the burner; G a longitudinally extending support on which the pilot is mounted, and H an electric heating element for igniting a jet of gas issuing from a jet. orifice H, the fiames thereof constituting a flare for igniting the pilot. The apparatus just described constitutes, as it were, the environment where the present invention has special utility.

The support G is a tube. Removably secured in one end of the tube, as by a screw Ill, is a block H having a flow passage therein to the inlet end of which is coupled a gas supply pipe I2 and to the outlet end of which is coupled a tube I3 the far end of which is removably supported in a block I4 in which the lower end of the pilot tube F is removably held by said tube I3 the latter having an orifice I5 in its upper side for discharge into the pilot tube. Should the orifice I5'require'cleaning, the tube I3 is withdrawn from the support G by releasing and withdrawing the block II at the outer end of the support.

Inside of the support G is a relatively lightweight lever I6 the pivot for which is indicated at ll. Secured to the lower side of the support is a switch-supporting panel or board I8, the switch comprising spring blades I9 and 20, the blade 20 being movable by the lever I6, and the blade I9 being adjustable with respect to the blade 20 by an adjusting screw 2 I. The switch forms part of the circuit for the motor M, the arrangement being such that unless the switch is closed, the motor cannot be energized. So long, however, as the thermostat is subject to the thermal conditions maintained by the burning pilot, the lever I6 is maintained at the limit of its counter-clockwise swing (Fig. 3), and the switch is in consequence maintained in circuit-closing position. This particular type of motor circuit is well known in the art.

The means for controlling the electricheating element H and for establishing a flow of gas from the jet orifice H adjacent thereto form no part of the present invention and therefore are not shown. It sufilces to say that toignite the pilot F, a flow of gas is first established to the pilot and then to the jet orifice H, as by a valve operating member K, said member also being operable to close the circuit for the heating element, said circuit being normally open. The main discharge outlet of the pilot is at the top thereof as indicated at F1. Extending downwardly from said outlet is a slit F2 and at thelower end of the latter is a circular port F3. An air supply port'F4 for the pilot is located in the lower portion of the pilot tube F in appropriate relation to the orifice IS. The flame resulting from the gas issuing from the orifice H ignites the gas issuing from the port Fa whereupon a line of flame along the slit F2 will ignite the gas issuing from the top outlet M as will now be readily understood.

The present invention provides an improved pilot-controlled thermostat for actuating the lever I6. In its preferred form, the thermostat comprises a rod 25 arranged to'be heated by flame resulting from the gas issuing from the lower port F3 of the pilot, the lower end of the rod coacting with the lever i5. 50 long as the pilot continues in lighted condition, flames will issue both from the outlet F1, to insure ignition oi the gas issuing from the main burner B, and from the port F3, to insure the expansion of the thermostat. The rod 25 ishoused for a portion of its length in a tube 26 the lower end of which latter is secured to the support G. The upper end of the rod is secured to the upper end of the tube 26 by means comprising a rod 21 which at its lower end is anchored to the top of the tube 26 as by alaterally extending block 28 and which at its upper end is anchored to the top of the rod 25 as by a cross piece 29. As shown in Fig. 5, the cross piece for connecting'the upper ends of the rods 25 and 21 may take the form of a bend 29'. However, the special cross piece 29 is preferred primarily because the rod 25 may then be adjustably secured with respect to the rod 21, it being noted that the rod 25 has a screw-thread connection with said cross piece, a lock nut being indicated at 30.

Located between the two rods 25 and 21 is a plate 3i for shielding the rod 21 from the flame issuing from the port I: in the pilot, it being noted that the plate is spaced from both of said rods. The plate is loosely confined between the upper and lower blocks 28 and", respectively,

so as not to interfere with the expansion of the rod 21. The preferred way of holding the plate in place is to provide a cut-out at each of its ends whereby to form fingers 32 which are confined in side notches 33 in the elements 28 and :29.

It will be readily appreciated that if the tube' 26 and the rods 25 and 21 all have the same coefficient of expansion and are at the same temperature, the expansion of the tubev 28 and the.

rod 21 will or should compensate for the expansion of a corresponding length of the rod 25 and thus render the rod 25 ineffective to actuate the lever it until the rod 25 is heated to ahigher degree than the rod 21. It therefore follows that the temperature in the furnace or other heated environment where the thermostat is located will not have such effect on the thermostat as to cause it to actuate the lever l; and that, in

order for the thermostat to actuate the said lever, the rod 25 must be specially heated, as by the flame from the gas issuing from the side port F; of the pilot. It also follows that, if the said flame were permitted to heat the rod 21 equally with the rod 25, the thermostat would not function. Hence the reason for interposing the plate 3| between andin spaced relation with respect to said rods.

For best results in operation, it is desirable that the tube 26 be made of material having a coefiicient of'expansion somewhat less than that of the rods 25 and 21, to compensate for conduction of heat from the specially heated portion of the rod 25 to that part thereof which is housed by the tube 26 and to the rod 21.

A pilot-controlled thermostat of the type described is obviously well adapted for use in environments where the temperature varies with the operation of a main heating burner, since changes in such temperature are automatically compensated for, thus making the operation of the thermostat wholly dependent on the heat of bination of a movable member and a support for the same, a thermostat for actuating said member and comprising two rods and a cross piece from which the rods extend in spaced relation and in the same direction to form a U-frame, the free end of one of said rods being anchored to said support and the free end of the other rod being operatively associated with said movable member to move it when a difference in expansion occurs between said rods, a burner adapted to discharge a jet of flame against that rod whose free end is associated with said movable member, and a flame-intercepting member between the rods.

2. In apparatus of the class described, the combination of a movable member and a support for the same, a thermostat for actuating said member and comprising two rods and a cross piece from which the rods extend in spaced relation and in the same direction to form a U- frame, the free end of one of said rods being anchored to said support and the free end of the other rod being operatively associated with said movable member to move it when a difference in expansion occurs between said rods, a burner having primary and secondary flame ports so arranged that flame from the secondary port will impinge on that rod whosefree end is associated with said movable member, and flame-interceptingmeans between said rods.

3. In apparatus of the class described, the combination of a movable member and a support for the same, a thermostat for actuating said member and comprising two rods and a cross piece from which the rods extend in spaced relation and in the same direction to form a U-frame,

the free end of one of said rods being anchored to said support by means including a tube whereinto the rod extends and the free end of the other rod being operatively associated with said'movable member for actuating it when a diflerence in expansion occurs between said rods, a burner arranged to discharge a jet of flame against one of said rods, and a flame-intercepting member between therods. a

4. In apparatus of the class described, the combination of a movable member and a support for the same, a thermostat for actuating said mem ber and comprising two rods and a cross piece from which the rods extend in spaced relation and in the same direction to form a U-frame, the free end of one of said rods being achored to said support and the free end of the other rod being operatively associated with said movable member to move itwhen a difierence in expansion occurs between said rods, a burner arranged to discharge a jet of flame against that rod whose free end is associated with said movable member, and a plate between said rods for intercepting the flow of flame across the space between them. I

5. The combination of a pilot having primary and secondary flame ports, a movable member, a thermostat for actuating said member and comprising two rods and a cross piece from which the rods extend in spaced relation and in the same direction whereby to form a U-frame, said pilot being so positioned with respect to one of said rods that flame from the secondary flame port will impinge upon the rod, and a flame-intercepting plate arranged between the rods.

- NEISON T. BRANCHE.

VILYNN O. BEAM. 

